Sound head for moving picture projectors



Aug. 11, 1936. I w. BAKER Y 2,050,480

SOUND HEAD FOR MOVING PICTURE PROJECTORS Filed May 5, 1955 ll V// v I l I INVENTOR fwvy WZaA e/r I. BY 7y 5 ATTORNEYS.

Patented Aug. 11, 1936 UNITED STATES ATENT OFFICE SOUND HEAD FOR MOVING PICTURE PROJECTORS 10 Claims.

This invention relates to moving picture projectors and particularly the sound head portion thereof and the primary object of this invention is the provision of a unique and novel sound head 5 structure wherein the exciter lamp and photoelectric cell are disposed in operative relation with the latter extending into a hollow drum around which passes the sound track film.

Another important aim of this invention is to ill-provide a sound head for moving picture projectors wherein the exciter lamp of the conventional type is housed within an air duct which has currents of air supplied thereto from a blower v fan which is preferably mounted within a hous- 15 ing in communication with the said air duct, and which is rotated by the passing of the sound track film through the sound head of the projector.

A yet further object of this invention is to provide in a sound head for moving picture projec- 20 tors, unique means for supporting the photoelectric cell so that it will be projected into a l hollow drum about which the sound track film travels, said drum being formed so as to allow the passage of light rays through the sound 25 track from the exciter.

A yet further object of this invention is to provide means for mounting a photo-electric cell so that it will be projected into a hollow drum about which the sound track film is wound, said 30 means for supporting the photo-electric cell being adapted to permit said cell to be swung to and from the operative position whereby threading of the sound track film might occur without difficulty and without having to actually disengage 35 the parts of the sound head assembly. 7

A large number of minor objects will appear during the course of the specification referring to the accompanying drawing wherein is shown in more or less diagrammatical manner a sound head embodying this invention.

In the drawing;

Figure 1 is a side elevation of a sound head for moving picture projectors illustrating one embodiment of this invention.

45 Fig. 2 is a cross section through the same taken on line II-II of Fig. 1.

Fig. 3 is a vertical irregular cross section through the sound head taken on line III-III of Fig. 2, and

50 Fig. 4 is a fragmentary condensed diagrammatical view illustrating the relationship between the photo-electric cell, sound track, optical system and the exciter lamp.

It is well known in this art that precision 5 work is required when locating the sound track oi a sound track film in the line of travel of the beam of light from exciter lamp to photo-eelctric cell, and difficulty has been experienced in maintaining the parts of the sound head in a fixed working position so that full and true undis- 5 torted sounds are produced at the loud speaker of the moving picture projecting system.

In addition to the foregoing, well known short comings of many sound heads for moving picture projecting machines, there has been found the additional difiiculty of maintaining the exciter lamp of the sound head properly cooled so that its heat will not afiect the film and other parts of the mechanism forming the sound head.

As has become apparent, this invention contemplates the provision of unique, novel and simple mechanism, and arrangement of parts which will be effective in partially, if not entirely, over-coming the well known dilficulties which have been inherent in sound heads.

In describing one embodiment of the invention as it is illustrated in the accompanying drawing reference will be made through the use of numerals and the number 6 designates a housing of any suitable form which may or may not be used when constructing the sound head. If the housing is used, the door 8 should be employed so as to allow quick access to the parts of the mechanism so that the sound track film I0 may be quickly passed through the sound head and threaded around the hereinafter described members. Film 10 may pass into and from housing 6 by way of apertures l2 and [4 respectively and the marginal perforations I6 formed in film l0 engage the radially extending sprocket teeth I8 which are carried by the main sound sprocket 20. This sprocket 20 is in association with a shaft 22 I journaled in bearing 24 secured to any suitable support and in some instances means for driving sprocket 20 is associated with shaft 22.

A specially formed bracket 26 is mounted within housing 6 and carries idler roller 28 which insures that the film ill will snugly fit the outer annular periphery of the hollow drum 30. Idler 28 is rotatably mounted and carried by bracket 26 through the medium of the integral yoke 32 and the laterally extending arm 34 having a swingable arm 36 is also supported by bracket 26. Arms 34 and 36 are hingedly inter-connected as at 38 so as to permit arm 36 to swing to and from an operative position where it supports the photo-electric cell 40 as shown in Fig. 3. Another integral arm 42 constitutes a part of bracket 26 and is designed to support the optical system unit 44 of the type which is usually interposed between the phot0-electric cell 30 and the exciter lamp 46.

Exciter lamp 46 is disposed in the flue portion 48 of an air duct 5b which is in connection with fan housing 52. The flue portion 48 extends vertically and has its upper end open and disposed so that air passing through the air duct 50 will be conveyed to a point exteriorly of housing 6. A window 54 adjacent exciter lamp 16 serves the purpose of allowing free passage of light rays and as the air currents pass upwardly through the fiue portion 48, additional air may be drawn through window 5% and past exciter lamp 46. A fan 56 having blades 58 is rotatably mounted within housing 52 and carried by shaft Gil which projects from one end of hollow roller 39 through a bearing 62 formed by bracket 26 and thence through housing 52 where it supports fan 56.

As film it is moved through the sound head it passes around idler roller 28 and then around drum 30 to sprocket 2E3. Sprocket teeth 63 formed on drum 38 may be employed to engage marginal perforations it in film ill and as the film it is move-d along through the sound head, fan 56 will be rotated at a sufficient speed as to create an appreciable amount of draft through duct 50 and thence through fiue portion 28 past exciter lamp :36. The exciter lamp will thereby be maintained at a temperature low enough to insure its long life and the heat which is created in the normal operation of the sound head will be automatically removed therefrom as the sound head is operated.

Photo-electric cell M! is mounted upon the swingable arm 36 and when this last mentioned arm is in position the photo-electric cell as will be projected into the hollow drum 3%. Drum 39 and photo-electric cell it should be in axial alignment and the sound track 64 formed on film ID will over-hang and partially circumscribe the photo-electric cell 4E3 so as to intersect the rays of light passing from the exciter lamp 46 through optical system i i. It is conceivable that drum 3!] might be otherwise formed so as to maintain sound track 5 3- in the path of travel of the aforesaid light rays but photo-electric cell 40 should be mounted so that as film ii) is threaded through the sound head nothing will interfere with quickly performing the threading operation. Swingably mounting photo-electric cell 46 upon arm 36 as indicated provides an effective way of embodying the invention in a sound head and such minor structural details as the spring 66 are contemplate-d by the invention.

The operation, advantages and combination of the sound head elements have all been rendered clear during the course of the foregoing specification and while the embodiment illustrated in the accompanying drawing has been clearly set down, it is desired to be limited only by the spirit of the invention and scope of the appendedclaims.

Having thus described the invention, what I claim as new and desired to be secured by Letters Patent is:

1. A sound head for moving picture projectors comprising in combination with the sound track film, a photo-electric cell; an exciter lamp; a fan operable by the movement of the film through the sound head and serving to maintain uniformity of speed of the film; and an air duct to direct air from the fan to the exciter lamp.

2. A sound head for moving picture projectors comprising, in combination with the sound track film, a photo-electric cell; an exciter lamp; a fan operable by the movement of the film through the sound head and serving to maintain uniformity of speed of the film; a housing for the fan; and an air duct in communication with the housing to receive air therefrom when the fan is in 5 motion, said exciter lamp being located within the said air duct.

3. A sound head for moving picture projectors comprising, in combination with the sound track film, a photo-electric cell; an exciter lamp; a fan operable by the movement of the film through the sound head and serving to maintain uniformity of speed of the film; a housing for the fan; and an air duct in communication with the housing to receive air therefrom when the fan is in motion, said exciter lamp being located within the said air duct, said air duct serving to support the exciter lamp in operative relation to the photo-electric cell and said track film.

4. A sound head for moving picture projectors comprising, in combination with the sound track film, a photo-electric cell; an exciter lamp; a fan operable by the movement of the film through the sound head and serving to maintain uniformity of speed of the film; a housing for the fan; and 25 an air duct in communication with the housing to receive air therefrom when the fan is in motion; said exciter lamp being located within the said air duct, said air duct terminating in a vertically disposed flue-portion having an upwardly 30 directed open end and a window formed in the wall thereof ajacent the said exciter lamp.

5. A sound head for moving picture projectors comprising, in combination with the sound track film, a photo-electric cell; an exciter lamp; a35 fan operable by the movement of the film through the sound head; means to conduct air from the fan to the exciter lamp to cool the same; and a series of rollers over which the said film travels, one of said rollers being hollow and having the said photo-electric cell projected thereinto, said fan serving to maintain uniformity of speed of the film over said hollow roller.

6. A sound head for moving picture projectors comprising, in combination with the sound track 45 film, a photo-electric cell; an exciter lamp; a fan operable by the movement of the film through the sound head; means to conduct air from the fan to the exciter lamp to cool the same; and a series of rollers over which the said film travels, one of said rollers being hollow and having the said photo-electric cell projected thereinto, said hollow roller and sound track film being relatively off-set whereby to cause the sound track of the film to overlie the said photo-electric cell, said fan serving to maintain uniformity of speed of the film over said hollow roller.

7. A sound head for moving picture projectors comprising, in combination with the sound track. film, a photo-electric cell; an exciter lamp; a fan operable by the movement of the film through the sound head; means to conduct air from the fan to the exciter lamp to cool the same; and-a hollow drum over which the said sound track film travels, said photo-electric cell being at least partially circumscribed by the walls of the hollow drum and said sound track, said fan serving to maintain uniformity of speed of the film over the hollow drum.

8. A sound head for moving picture projectors 70 comprising, in combination with the sound track film, a photo-electric cell; an exciter lamp; afan operable by the movement of the film through the sound head; means to conduct air from the fan to the exciter lamp to cool the same; and a drum in juxtaposition to the said photo-electric cell, said drum being formed to guide the sound track of said film through a path of travel between the photo-electric cell and exciter lamp whereby light rays pass uninterruptedly from the latter to the former, said fan serving to maintain uniformity of speed of the film over the hollow drum.

9. A sound head for moving picture projectors comprising, in combination with the sound track film, a photo-electric cell; an exciter lamp; an optical system interposed between said exciter lamp and photo-electric cell to direct rays of light from the former to the latter through the sound track of the said film; a fan operable by the movement of the film through the sound head; means to conduct air from the fan to the exciter lamp to cool the same; and a hollow drum over which passes the said film, said photo-electric cell extending into the said hollow drum; said drum being formed to maintain the sound track of the said film in the path of said rays of light passing from the exciter lamp to the photo-electric cell as the film moves through the sound head, said fan serving to maintain uniformity of speed of the film over the hollow drum.

10. A sound head for moving picture projectors comprising, in combination with the sound track film, a photo-electric cell; an exciter lamp; an optical system between the photo-electric cell and exciter lamp; a fan having a drive shaft serving to maintain uniformity of speed of the film; an air duct to receive air from the fan; a hollow drum mounted on the drive shaft of the fan over which the said film passes; and means for removably supporting the said photo-electric cell in an operative position projected into the said hollow drum, said film being passed over said drum with its sound track projected over said photo-electric cell, said fan being operated by the passing of the film through the sound head, and said exciter lamp being positioned within the said air duct to be cooled by air passing there- 20 through.

HARRY W. BAKER. 

